Ferrule holding structure for optical connector component

ABSTRACT

Disclosed is an optical connector component  31  comprising a ferrule  2  for receiving an end portion of a core optical fiber of a fiber optic cable, a flange  32  mounted on the peripheral of the ferrule  2,  and a one-piece plug frame  33  for floatingly supporting the ferrule  2  having the flange  32  mounted thereon. The flange  32  and the plug frame  33  are provided with respective engagement portions  37, 50  that are mutually engaged. The flange  32  has such resiliency that it is reduced in diameter by a radial and inward force exerted through the engagement portions  37, 50  when the ferrule  2  is inserted into the plug frame  33  from one end thereof and the flange  32  is restored to the original condition present before the insertion when the engagement portions  37, 50  are mutually engaged.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a ferrule holding structure foran optical connector component for use in connection between fiber opticcables.

[0003] 2. Description of the Related Art

[0004] In general, in an optical communication system, several types ofoptical connector components have been used for detachably connectingbetween one fiber optic cable and another fiber optic cable or otheroptical device. One example of such optical connector components is anoptical attenuator that is disclosed in TOKKOHEI No. 5-45924. Suchoptical attenuator is designed to have optical connectors mounted onboth sides thereof so that an optical signal is relayed and attenuatedbetween those optical connectors.

[0005] One such conventional type attenuator 1 is illustrated in FIG. 4.Referring to this figure, the optical attenuator 1 includes a ferrule 2for receiving a core optical fiber at the center thereof, a connectionsleeve 3 for an attenuation film 61 affixed to an outer middle portionof the ferrule 2, a split sleeve 4 affixed to an outer rear end portionof the ferrule 2, a first plug frame 5 for surrounding and holding afront end portion of the ferrule 2, a second plug frame 6 forsurrounding and holding an opposite rear end portion of the ferrule 2,and a housing member 7 for accommodating the first and second plugframes 5 and 6.

[0006] The ferrule 2 is made of some ceramic material such as zirconiaand has an axially elongated cylindrical form on which the attenuationfilm 61 is deposited for attenuating the passage of light.

[0007] The connection sleeve 3 is made of some metal material such ascupper alloy in the form of a hollow cylinder that is affixed to theferrule 2 with an adhesive. A flange 8 is affixed on an outer peripheralof the ferrule 2 adjacent a front end of the sleeve 3. The flange 8 ismade of metal and has predetermined number of grooves (not shown) formedon an outer surface thereof.

[0008] The split sleeve 4 is made of zirconia, for example, in the formof a hollow cylinder and is axially split to provide resiliency. Thesplit sleeve 4 has a front end surface that is contact with the rear endsurface of the connection sleeve 3, and an opposite rear end surfacethat is backwardly projected beyond the rear end surface of the ferrule2.

[0009] The first plug frame 5 is made of some plastic material, forexample, and it is generally in the form of a cubic in which acylindrical cavity 9 is axially formed. An inner brim 10 is formed atthe inner center portion of the first plug frame 5 and has keys providedat the rear end portion thereof in corresponding to the grooves in theflange 8. Thereby, the ferrule 2 having the connection sleeve 3 mountedthereon is prevented from falling off the front end of the attenuator 1.A first engagement portion 12 is formed on and projected from an outersurface of the first plug frame 5, and a protrusion 13 is formed on therear portion of the first engagement portion 12. In addition, latchholes 14 are formed at positions opposite to each other on the rearportion of the first plug frame 5, and elongated cutouts (not shown) arealso formed at another positions opposite to each other to extend fromthe rear end of the first plug frame 5.

[0010] The second plug frame 6 is made of some plastic material, forexample, and includes, a cylindrical holding portion 16 in axialdirection and a pair of thin plate-like resiliently deformable portions17 that extend in cantilevered manner from the middle portion of theholding portion 16 toward the rear end of the attenuator 1. Each of thedeformable portions 17 has its rear end portion inwardly projected toform a second engagement portion 18. The holding portion 16 has itsouter surface on which latch projections 19 are formed at the positionscorresponding to the latch holes 14, and its inner surface on which ashoulder 20 is formed at the middle portion thereof. The holding portion16 further includes an inwardly projecting fall-off prevention portion21 formed on the rear end portion thereof for preventing the ferrule 2fixed to the split sleeve 4 from falling off the holding portion 16.

[0011] The housing member 7 is made of stainless steel, for example, andincludes a front end portion 22 that is mated with an adapter (notshown) and a rear end portion 23 with which a plug (not shown) is mated.The front end portion 22 has such width that is smaller than that of therear end portion 23 so that there is a difference in width producedtherebetween. An opening 24 is provided on each of both sidewalls of thefront end portion 22. Accordingly the first engagement portion 12 andthe protrusion 13 may cause an axial floating movement along theopenings 24. In addition, a key projection 25 is formed on an outersurface of the front end portion 22, and the corresponding guide recess26 is formed in the sidewall of the rear end portion 23 so that itaxially extends from the rear end thereof.

[0012] Now, the process of assembling the prior art optical attenuator 1having the configuration as above will be described.

[0013] The connection sleeve 3 is affixed to the ferrule 2 with anadhesive. Then, the flange 8 is affixed so that it is contact with thefront end surface of the connection sleeve 3. The split sleeve 4 ispress-fitted so that it is contact with the rear end surface of theconnection sleeve 3. Thereafter, the front end portion of the ferrule 2having the connection sleeve 3, the split sleeve 4 and the flange 8mounted thereon is inserted into the cavity 9 of the first plug frame 5from the rear side thereof In this connection, the groove (not shown) onthe flange 8 is mated with the key 11 of the first plug frame 5 so thatthe flange 8 abuts the brim 10. Then, the second plug frame 6 isinserted into the first plug frame 5 in such manner that the holdingportion 16 of the second plug frame 6 surrounds the rear end portion ofthe split sleeve 4. Thereafter, the second plug frame 6 is furtherinserted until the latch projection 19 snaps into the latch hole 14 uponwhich the second plug frame 6 is coupled to the first plug frame 5. Inthis condition the ferrule 2 may floatingly be moved in the axialdirection between the inner brim 10 of the first plug frame 5 and theshoulder 20 of the second plug frame 6. Finally the first and secondplug frames 5 and 6 coupled together are inserted into the housingmember 7 from the rear side thereof until the first engagement portion12 and the protrusion 13 become received in the opening 24. Accordingly,the first and second plug frames 5 and 6 are held in the housing member7, but they may floatingly be moved in the axial direction.

[0014] The optical attenuator 1 that is assembled in the manner as aboveis then connected as follows: When the front end portion 22 is matedwith the adapter (not shown) so that the key projection 25 is receivedin the guide recess (not shown) of the adapter, then the firstengagement portion 12 is engaged with the adapter. On the other hand,when the rear end portion 23 is mated with the plug (not shown) so thatthe key projection (not shown) of the plug is received in the guiderecess 26, then the second engagement portion 18 is engaged with theplug. As the result, the plug is connected with the adapter through theoptical attenuator 1.

[0015] However, the prior art optical connector components such as thoseincluding the optical attenuator 1 as described above are generallydefective in that they need great number of parts and assembling steps,and involves many laborious works because of the sleeve 3 and the flange8 made of metal. In addition, they are difficult to reduce themanufacturing cost.

[0016] Because an adhesive is used for affixing the connection sleeve 3to the ferrule 2, any excessive amount of adhesive that has come out ofthe end of the connection sleeve 3 flows into between connection sleeve3 and the split sleeve 4 or the flange 8, which may cause deteriorationin precision of the length between the flange 8 and the split sleeve 4.Therefore, it is difficult to improve in precision of size and yield ofthe product in the prior art.

[0017] In view of the above an object of the present invention is toprovide a ferrule holding structure that can reduce the number of partsand assembling steps, improve in precision of size and yield of theproduct, and reduce the manufacturing cost of the product.

SUMMARY OF THE INVENTION

[0018] To attain such object the present invention provides an opticalconnector component comprising a ferrule for receiving an end portion ofa core optical fiber of a fiber optic cable, a flange mounted on theperipheral of the ferrule, and a one-piece plug frame for floatinglysupporting the ferrule having the flange mounted thereon, in which theflange and the plug frame are provided with respective engagementportions that are mutually engaged, and in which the flange has suchresiliency that it is reduced in diameter by a radial and inward forceexerted through the engagement portions when the ferrule is insertedinto the plug frame from one end thereof and the flange is restored tothe original condition present before the insertion when the engagementportions are mutually engaged.

[0019] Preferably the flange is provided with an adhesive injection holein the peripheral wall thereof and an enlarged diameter recess portionat one end thereof, and when an adhesive is injected into the adhesiveinjection hole after the flange is mounted on the ferrule, then theadhesive flows between the flange and the ferrule and reaches theenlarged diameter recess portion.

[0020] Furthermore, a clearance is produced between the flange and theferrule, and when the ferrule having the flange mounted thereon isinserted into the plug frame from one end thereof, the flange is reducedin diameter due to the presence of the clearance. The flange is made ofresin material.

[0021] Such construction of the present invention allows reduction innumber of parts and assembling steps for the optical connectorcomponent, facilitated assembly works, improvement in precision of size,and reduction of manufacturing cost. In addition, there is substantiallyno possibility that an adhesive used for affixing the flange to theferrule comes out of the end of the flange, which is effective toimprove in precision of size and yield of the product.

BRIEF DESCRIPTION OF THE INVENTION

[0022] Now, the present invention will be described with reference tothe accompanying drawings, in which:

[0023]FIG. 1 is an enlarged view of an optical attenuator according toan embodiment of the present invention, illustrating an upper half ofthe attenuator in cross section;

[0024]FIG. 2 is an enlarged view showing a flange according to theembodiment of the present invention partially in cross section;

[0025]FIG. 3 is an enlarged view of a plug frame according to theembodiment of the present invention, illustrating an upper half of theplug frame in cross section; and

[0026]FIG. 4 is an enlarged view of an optical attenuator in the priorart, illustrating an upper half of the attenuator in cross section.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0027] The present invention will be described in more detail withreference to FIGS. 1 to 3 illustrating an optical attenuator 31constructed according an embodiment of the present invention. For thepurpose of simplification, the parts corresponding to that of the priorart optical attenuator 1 are indicated by the same reference numbers andthe description regarding such parts are omitted.

[0028]FIG. 1 is an enlarged view of an optical attenuator 31 accordingto an embodiment of the present invention, illustrating an upper half ofthe attenuator in cross section. The optical attenuator 31 includes aferrule 2 having an attenuation film or an attenuation fiber providedthereon, a flange 32 affixed to an outer peripheral at the middleportion of the ferrule 2, a split sleeve 4, a plug frame 33 forsupporting the ferrule 2 on which the flange 32 and the split sleeve 4are affixed, and a housing member 7.

[0029]FIG. 2 is an enlarged view showing the flange 32 partially incross section. The flange 32 is made of plastic material in the form ofa cylinder having the wall thickness greater than that of the splitsleeve 4. A press-fit portion 34 having the minimum inner diameter isformed in the middle portion of the flange 32. The ferrule 2 ispress-fitted to this press-fit portion 34. The flange 32 furtherincludes a deformable portion 35 positioned near the front end thereofand an adhesion portion 36 positioned near the rear end thereof Thedeformable portion 35 and the adhesion portion 36 have respective innerdiameter greater than that of the outer diameter of the ferrule 2.

[0030] The deformable portion 35 has the predetermined number (two inFIG. 2) of engagement projections 37 formed on the outer surfacethereof. Each of the engagement projections 37 has a tapered portion atthe rear side. The deformable portion 35 further has the predeterminednumber (for example, four) of axial slits 38 formed in the peripheralwall thereof. The axial slit 38 is in the form of a triangle whose acuteangled apex is pointed to rear side. A front end 39 of the deformableportion 35 has the maximum inner diameter so that there is a taperedsurface 40 produced between the front end 39 and the press-fit portion34. When the flange 32 is mounted to the ferrule 2, a clearance 60 isproduced between the deformable portion 35 and the ferrule 2. Theadhesion portion 36 has the predetermined number (two in FIG. 2) ofcircular adhesive injection holes 41 formed in the peripheral wallthereof. An enlarged diameter recess portion 42 is formed on an innersurface of the flange 32 at the rear end thereof When the flange 32 ismounted to the ferrule 2, a clearance 57 is produced between theadhesion portion 36 and the ferrule 2.

[0031]FIG. 3 is an enlarged view of the plug frame 33, illustrating anupper half of the plug frame in cross section. The plug frame 33 is madeof plastic material, for example, and includes a cylindrical holdingportion 43 in axial direction and a pair of resiliently deformableportions 44 that extend in cantilevered manner from the rear end portionof the holding portion 43 toward the rear side of the attenuator 31. Theholding portion 43 is designed to floatingly hold the ferrule 2 havingthe flange 32 and the split sleeve 4 mounted thereon. The holdingportion 43 is integral with the resiliently deformable portions 44.

[0032] The holding portion 43 is divided into the following sectionsdepending on the wall thickness: a first thin wall section 45; a middlewall thickness section 46; a thick wall section 47; and a second thinwall section 48. A first engagement portion 49 is formed on the outersurface of the first thin wall section 45, a square engagement hole 50is formed in the middle wall thickness section 46, and a protrusion 51is formed on the outer surface near the engagement hole 50. The outersurface of the holding portion 43 between the first thin wall section 45and the middle wall thickness section 46, and the front side of theprotrusion 51 are outwardly slanted. The inner surface of the holdingportion 43 is provided with a first shoulder portion 52 between thefirst thin wall section 45 and the middle wall thickness section 46, anda second shoulder portion 53 between the middle wall thickness section46 and the thick wall section 47. The inner diameter of the holdingportion 43 is reduced stepwise from the first thin wall section 45toward rear side of the optical attenuator 31. An inwardly projectingfall-off prevention portion 54 is formed on the rear end of the secondthin wall section 48. The fall-off prevention portion 54 has its innerdiameter that is smaller than the outer diameter of the split sleeve 4,but greater than the outer diameter of the ferrule 2. The length betweenthe second shoulder portion 53 and the fall-off prevention portion 54 isgreater than that of the split sleeve 4. Each of the pair of resilientlydeformable portions 44 includes a resilient arm 55 extending incantilevered manner from the rear end portion of the deformable portion44 toward the front side of the attenuator 31. The resilient arm 55 isprovided with a second inwardly projecting engagement portion 56 at thefront end thereof. Because the first engagement portion 49 and thesecond engagement portion 56 are formed on one and same plug frame 33,it becomes easy to control the length between the first engagementportion 49 and the second engagement portion 56 and to allow improvementin precision of the size.

[0033] Next, the process of assembling the optical attenuator 31 will bedescribed in more detail.

[0034] The ferrule 2 is press-fit to the flange 32 and is held in thepress-fit portion 34 of the flange 32. Then the predetermined amount ofadhesive is injected via the adhesive injection hole 41 into the flange32. The adhesive fills the clearance 57 and reaches the enlargeddiameter recess portion 42. Because the enlarged diameter recess portion42 has the inner diameter that is greater than that of the remainingportion of the adhesion portion 36, there is substantially nopossibility that the adhesive that has reached the enlarged diameterrecess portion 42 would leak to anywhere at the rear side thereof.

[0035] Thereafter, the ferrule 2 having the flange 32 mounted thereon isinserted into the split sleeve 4. The front end surface of the splitsleeve 4 abuts the rear end surface of the flange 32 and the rear endportion of the split sleeve 4 backwardly projects beyond the rear end ofthe ferrule 2. Because of the wall thickness of the flange 32 greaterthan that of the split sleeve 4, a shoulder portion 58 is providedbetween the flange 32 and the split sleeve 4. Because of no possibilitythat the adhesive would be leaked from the rear end of the flange 32, asdescribed above, the split sleeve 4 intimately abuts the flange 32without any clearance therebetween. Accordingly the fixed length canalways be assured between the front end surface of the flange 32 and therear end surface of the split sleeve 4, which allows improvement inprecision of size of the product.

[0036] Next, the ferrule 2 having the flange 32 and the split sleeve 4mounted thereon is inserted into the holding portion 43 of the plugframe 33 from the front side thereof, as described earlier. Theengagement projection 37 of the flange 32 has the tapered outer surfaceformed at the rear side thereof, and therefore, it is smoothly slidalong the inner surface of the first thin wall section 45 of the plugframe 33 to apply a radial and inward force to the deformable portion35. Because there is the clearance 60 present between the deformableportion 35 and the ferrule 2, and the predetermined number of the slits38 formed in the flange 32, the deformable portion 38 is graduallyreduced in diameter. As the ferrule 2 is further inserted into theholding portion 43, the engagement projection 37 abuts the inner surfaceof the middle wall thickness section 46, after passing through the firstshoulder portion 52. Because the middle wall thickness section 46 hasits inner diameter that is smaller than that of the first thin wallsection 45, the deformable portion 35 is further reduced in diameter.Thereafter, the engagement projection 37 snaps into the engagement hole50 and the deformable portion 35 restores the original condition whereit was before insertion. Now, the ferrule 2 having the flange 32 and thesplit sleeve 4 mounted thereon is floatingly supported in the holdingportion 43 of the plug frame 33. In this condition any movement of theferrule 2 in the direction toward the front side is restricted due tothe abutment between the front end surface of the engagement projection37 and a front side surface 59 of the engagement hole 50. On the otherhand, any movement of the ferrule 2 in the opposite direction toward therear side is restricted due to the abutment between the shoulder portion58 and the second shoulder portion 53 because of the length between thesecond shoulder portion 53 and the fall-off prevention means 54 greaterthan that of the split sleeve 4. Accordingly, in view of the fact thatthe front side surface 59 of the engagement hole 50 and the secondshoulder portion 53 are formed on one and same plug frame 33, the lengththerebetween, or in other word, an extent of floating movement, caneasily be controlled, and consequently, improvement in precision of sizecan be attained. Furthermore, there is substantially no possibility thatthe split sleeve 4 is broken or damaged when it is collided to thefall-off prevention means 54.

[0037] Next, the plug frame 33 having the ferrule 2 contained therein isinserted into the housing member 7 from the rear side thereof. The firstengagement portion 49 and the protrusion 51 are received in the opening24 so that the plug frame 33 is axially floatingly supported in thehousing member 7.

[0038] In the embodiment as above, the optical attenuator has beendescribed by way of an example. The present invention, however, is notlimited to such optical attenuator, but may applied to any other opticalconnector components such as a filter, a terminator, etc.

[0039] The flange 32 and the plug frame 33 may include any other mutualengagement portion than that described above. For example, as opposed tothe embodiment as described above, the engagement projection 37 may beformed on the plug frame 33 and the engagement hole 50 may be formed inthe flange 32.

[0040] In addition, the present invention may be configured in suchmanner that the ferrule 2 having the flange 32 mounted thereon isinserted into the plug frame 33 from the rear side thereof.Alternatively the flange 32 may be formed in which the deformableportion 35 is positioned at the rear side to the press-fit portion 34and the adhesion portion 36 is positioned at the front side to thepress-fit portion 34.

[0041] It is apparent from the forgoing that a plug frame is configuredas a one-piece component, a flange is made of resin material and has anengagement portion formed thereon, and a ferrule is held in the plugframe simply by inserting the ferrule having the flange mounted thereoninto the plug frame from one side thereof. Therefore, it is possible toreduce the number of component parts and assembling steps, to simplifythe assembling operations and to reduce the manufacturing cost.

[0042] Furthermore, because of an enlarged diameter recess portionformed at the end of the flange, there is substantially no possibilitythat an adhesive used for affixing the flange to the ferrule comes outof the end of the flange, which allows improvement in precision of sizeand yield of the product.

What is claimed is:
 1. An optical connector component comprising aferrule for receiving an end portion of a core optical fiber of a fiberoptic cable, a flange mounted on the peripheral of the ferrule, and aone-piece plug frame for floatingly supporting the ferrule having theflange mounted thereon, a ferrule holding structure comprising theflange and the plug frame, characterized in that: the flange and theplug frame are provided with respective engagement portions that aremutually engaged; and the flange has such resiliency that it is reducedin diameter by a radial and inward force exerted through the engagementportions when the ferrule is inserted into the plug frame from one endthereof and the flange is restored to the original condition presentbefore the insertion when the engagement portions are mutually engaged.2. A ferrule holding structure according to claim 1 in which the flangeis provided with an adhesive injection hole in the peripheral wallthereof and an enlarged diameter recess portion at one end thereof, andwhen an adhesive is injected into the adhesive injection hole after theflange is mounted on the ferrule, then the adhesive flows between theflange and the ferrule and reaches the enlarged diameter recess portion.3. A ferrule holding structure according to claim 1 or 2 in which aclearance is produced between the flange and the ferrule, and when theferrule having the flange mounted thereon is inserted into the plugframe from one end thereof, the flange is reduced in diameter due to thepresence of the clearance.
 4. A ferrule holding structure according toclaim 3 in which the flange is made of resin material.